1. Field of the Invention
The present invention relates to a shingling algorithm, and more particularly, to a shingling algorithm for edge printing.
2. Description of the Related Art
In a conventional printing apparatus as shown in FIG. 1, a sheet of printing paper 11 is fed between a paper feed roller 12 and a pressure roller 14 in a paper feed direction perpendicular to a scanning direction in which the printing paper 11 is scanned as indicated by an arrow of the scanning direction. While the printing paper 11 is moved beneath a head 15, ink is discharged through a nozzle (not shown) of an ink cartridge (not shown) mounted on the head 15 for printing. The head 15 reciprocates in the scanning direction perpendicular to the paper feed direction in which the printing paper 11 is supplied, while the ink is discharged. The printing paper 11 after printing is output from the printing apparatus by a paper exit roller 16 and a star wheel 18.
FIG. 2 shows the printing paper 11 after printing using a conventional method performed in the conventional printing apparatus as described with reference to FIG. 1. As shown in FIG. 2, when a printing command is input to the conventional printing apparatus, data are printed only in a region E of the printing paper 11, not in edge regions A, B, C, and D. In other words, the data cannot be printed in the edge regions A, B, C, and D with the conventional printing apparatus even when a user designates all edge margins to zero.
To improve this problem, an apparatus for and method of edge printing without roller contamination are disclosed in U.S. Patent No. 2002/0070991 A1.
FIG. 3 is a sectional view of a conventional printing apparatus disclosed in U.S. Patent No. 2002/0070991 A1. Referring to FIG. 3, a sheet of printing paper P is transferred in a sub-scanning direction (paper feed direction) while supported by paper feed rollers 25a and 25b. When a front edge of the printing paper P passes between paper exit rollers 25c and 25d, a back (bottom or rear) edge Pr of the printing paper P reaches a front rib 26f and a flatten 26. At this time, ink Ip is discharged from a head 28 for back edge printing. The head 28 includes a plurality of nozzles (#1-#8). Since the back edge printing is initiated before the back edge Pr of the printing paper P reaches the last nozzle #8, the back edge printing can be achieved without leaving a margin at the back edge Pr of the printing paper P even when the printing paper P is improperly fed. Ink droplets discharged out toward the printing paper P are absorbed by an absorption member 27f. The conventional printing apparatus further includes another rib 26r and another absorption member 27r. Although this method enables printing in upper, lower, left, and right margins of the printing paper P, there is a need for high quality edge printing using software, such as a shingling algorithm.